U.S. patent number 10,385,470 [Application Number 14/386,686] was granted by the patent office on 2019-08-20 for treatment of an anodically oxidized surface.
This patent grant is currently assigned to Nanogate AG. The grantee listed for this patent is Nanogate AG. Invention is credited to Anne Danzebrink, Rolf Danzebrink, Tanja Geyer, Markus Koch.
United States Patent |
10,385,470 |
Danzebrink , et al. |
August 20, 2019 |
**Please see images for:
( Certificate of Correction ) ** |
Treatment of an anodically oxidized surface
Abstract
The invention relates to a process for treating an anodically
oxidized surface of aluminum or an aluminum alloy by means of a wet
chemical process, wherein the surface of aluminum or the aluminum
alloy is pretreated, anodically oxidized, flushed and partially
subjected to hot compacting. The present invention also relates to
a corresponding aluminum surface obtainable, in particular, with
the aid of the process according to the invention.
Inventors: |
Danzebrink; Rolf (Ingbert,
DE), Danzebrink; Anne (Ingbert, DE), Geyer;
Tanja (Schonenberg-Kubelberg, DE), Koch; Markus
(Pirmasens, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Nanogate AG |
Quierschied-Gottelborn |
N/A |
DE |
|
|
Assignee: |
Nanogate AG
(DE)
|
Family
ID: |
47988969 |
Appl.
No.: |
14/386,686 |
Filed: |
March 21, 2013 |
PCT
Filed: |
March 21, 2013 |
PCT No.: |
PCT/EP2013/055913 |
371(c)(1),(2),(4) Date: |
September 19, 2014 |
PCT
Pub. No.: |
WO2013/139899 |
PCT
Pub. Date: |
September 26, 2013 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
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US 20150034487 A1 |
Feb 5, 2015 |
|
Foreign Application Priority Data
|
|
|
|
|
Mar 22, 2012 [DE] |
|
|
10 2012 204 636 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C
18/122 (20130101); C23C 18/1254 (20130101); C23C
18/1245 (20130101); C25D 11/24 (20130101); C25D
11/246 (20130101); C25D 11/18 (20130101); C25D
11/16 (20130101) |
Current International
Class: |
C25D
11/18 (20060101); C25D 11/16 (20060101); C23C
18/12 (20060101); C25D 11/24 (20060101) |
Field of
Search: |
;205/201-204,229 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1306467 |
|
May 2003 |
|
EP |
|
1407935 |
|
Apr 2004 |
|
EP |
|
1780313 |
|
Jul 2006 |
|
EP |
|
2328183 |
|
Jun 2011 |
|
EP |
|
60-179475 |
|
Sep 1985 |
|
JP |
|
06-316787 |
|
Nov 1994 |
|
JP |
|
2002-069696 |
|
Mar 2002 |
|
JP |
|
WO 2011001862 |
|
Jan 2011 |
|
JP |
|
2009/068168 |
|
Jun 2009 |
|
WO |
|
2011/020556 |
|
Feb 2011 |
|
WO |
|
Other References
English translation of WO2011/001862 from CN102713021. cited by
examiner .
http://aluminumsurface.blogspot.com/2009/04/why-sealing-process-is-so-innp-
ortant.html (Year: 2009). cited by examiner .
May 13, 2014 International Search Report issued in International
Application No. PCT/EP2013/055913. cited by applicant.
|
Primary Examiner: Cohen; Brian W
Attorney, Agent or Firm: Hudson; Seth L. Clements Bernard
Walker, PLLC
Claims
The invention claimed is:
1. A process for treating an anodically oxidized surface of
aluminum or an aluminum alloy having a thickness of from 5 to 15
.mu.m by means of a wet chemical process, wherein the surface of
aluminum or of an aluminum alloy is pretreated, anodically
oxidized, rinsed and partially hot-sealed in fully desalted water
with a pH value of 6+/-0.5 or to a treatment with saturated steam
above 98.degree. C., thus forming a conversion layer comprising
AlO(OH) on said pretreated, anodically oxidized, rinsed and
partially hot-sealed surface of aluminum or aluminum alloy, said
conversion layer having pores that are not completely closed
characterized in that partial hot sealing is performed in a
solution consisting of fully desalted water at a temperature
greater than 96.degree. C. up to 100.degree. C. or to a treatment
with saturated steam above 98.degree. C. in the course of up to 30
s/.mu.m of layer thickness of the conversion layer, followed by
contacting the conversion layer with a material containing an
organosilicon network former, thus completely closing said pores,
followed by curing at a temperature of up to 250.degree. C.
resulting in a colorless aluminum surface containing Al--O--Si
bonded organosilicon functional silicates, wherein the Al--O--Si
bonds are in and on the conversion coating, and exhibiting alkali
resistance up to pH values of 13.5.
2. The process according to claim 1, characterized in that said
pretreatment includes degreasing, rinsing, pickling, rinsing,
polishing, rinsing, acid treatment, and rinsing.
3. The process according to claim 1, characterized in that said
material is contacted with said anodically oxidized surface by flow
coating, dipping, spraying, rolling, knife coating and/or roller
coating.
4. The process according to claim 1, characterized in that the
material and/or the conversion layer is charged electrostatically
before and/or during the contacting.
5. The process according to claim 1, characterized in that said
partial hot sealing is performed in the course of up to 20 s/.mu.m
of layer thickness of the conversion layer.
6. The process according to claim 1, characterized in that a
material is employed that contains one or more organically modified
silanes selected from the group of non-fluorinated silanes,
selected from CH.sub.3Si(OC.sub.2H.sub.5).sub.3,
C.sub.2H.sub.5Si(OC.sub.2H.sub.5).sub.3,
CH.sub.3Si(OCH.sub.3).sub.3, C.sub.6H.sub.5Si(OCH.sub.3).sub.3,
C.sub.6H.sub.5Si(OC.sub.2H.sub.5).sub.3,
CH.sub.2.dbd.CHSi(OOCCH.sub.3).sub.3,
CH.sub.2.dbd.CHSi(OCH.sub.3).sub.3,
CH.sub.2CHSi(OC.sub.2H.sub.5).sub.3,
CH.sub.2.dbd.CHSi(OC.sub.2H.sub.4OCH.sub.3).sub.3,
CH.sub.2.dbd.CHCH.sub.2Si(OCH.sub.3).sub.3,
CH.sub.2CHCH.sub.2Si(OC.sub.2H.sub.5).sub.3,
CH.sub.2.dbd.CHCH.sub.2Si(OOCCH.sub.3).sub.3,
CH.sub.2.dbd.C(CH.sub.3)COOC.sub.3H.sub.7Si(OCH.sub.3).sub.3,
CH.sub.2.dbd.C(CH.sub.3)COOC.sub.3H.sub.7Si(OC.sub.2H.sub.5).sub.3,
(C.sub.2H.sub.50).sub.3SiC.sub.6H.sub.4NH.sub.2,
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6NH.sub.2,
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6CN,
(CH.sub.3O).sub.3SiC.sub.4H.sub.8SH,
(CH.sub.3O).sub.3SiC.sub.6H.sub.12SH,
(CH.sub.3O).sub.3SiC.sub.3H.sub.6SH,
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6SH,
(CH.sub.3O).sub.3SiC.sub.3H.sub.6NHC.sub.2H.sub.4NH.sub.2,
(CH.sub.3O).sub.3SiC.sub.3H.sub.6NHC.sub.2H.sub.4NHC.sub.2H.sub.4NH.sub.2-
, ##STR00002## and/or fluorinated silanes, selected from
CF.sub.3CH.sub.2CH.sub.2SiY.sub.3,
C.sub.2F.sub.5CH.sub.2CH.sub.2SiY.sub.3,
C.sub.4F.sub.9CH.sub.2CH.sub.2SiY.sub.3,
n-C.sub.6F.sub.13CH.sub.2CH.sub.2SiY.sub.3,
n-C.sub.8F.sub.17CH.sub.2CH.sub.2SiY.sub.3,
n-C.sub.10F.sub.21CH.sub.2CH.sub.2SiY.sub.3, where Y represents
OCH.sub.3 and/or OC.sub.2H.sub.5.
7. The process according to claim 1, characterized in that said
curing is performed at a temperature within a range of from 120 to
200.degree. C.
8. The process of claim 1, wherein said partial hot sealing is
performed in a solution consisting of fully desalted water at a
temperature greater than 96.degree. C. up to 100.degree. C. for up
to 20 s/.mu.m.
Description
FIELD OF THE INVENTION
The invention relates to a process for treating an anodically
oxidized surface of aluminum or an aluminum alloy by means of a wet
chemical process, wherein the surface of aluminum or of the
aluminum alloy is pretreated, anodically oxidized, rinsed and
hot-sealed.
The present invention further relates to a corresponding aluminum
surface obtainable, in particular, by means of the process
according to the invention.
The term "aluminum" as used hereinafter also includes aluminum
alloys according to the invention. Aluminum alloys are known to be
produced by alloying aluminum with other metals, for example,
manganese, magnesium, copper, silicon, nickel, zinc and beryllium.
In most cases, Al 99.5 (pure aluminum) serves as the starting
material for the alloys.
BACKGROUND OF THE INVENTION
EP 1 407 935 A1 and the related patent family describes a process
for applying a thin ceramic coating material to a surface of a
motor vehicle assembling element made of aluminum, which is to be
coated, wherein said aluminum is anodized before being coated, and
a roughness of the surface to be coated for adhesion of the coating
material is achieved by said anodizing process. Then, said thin
ceramic coating material, which exclusively consists of inorganic
components, is applied by means of an electrostatic application
method or by means of a wet-chemical application method at an
almost constant layer thickness as a coating with a pore-free and
closed surface.
This technical teaching is based on the object of improving the
quality of known thin ceramic coatings. In particular, a process is
to be provided that enables a cost efficient production of high
quality thin ceramic coatings. In addition, parts or objects that
have a high quality thin ceramic coating and can be produced cost
efficiently are to be created. It is further essential that the
thin ceramic coating exclusively consists of inorganic components.
The description of the process ends with the application of the
coating to the aluminum surface.
WO 2009/068168 A2 and the related patent family describe a
component made of aluminum and/or an aluminum alloy, particularly a
decorative or functional part, having very high corrosion
resistance, and to a method for the production thereof. The
conversion layer is to be sealed in the course of at least 3
min/.mu.m of layer thickness. The high corrosion resistance,
particularly high alkali resistance, is to be achieved in that the
surface of the component comprises an oxide layer created evenly by
anodization and a cover layer sealing and evenly covering the
porous oxide layer. The cover layer is created by an oxide layer
hydrate compound sealing the pores of the oxide layer and by an
additional inclusion of glass-like substances and application
thereof to the oxide layer at the same time. A compound of one or
more alkali silicates is proposed as said glass-like substances.
Alternatively, the cover layer may also comprise exclusively
aluminum oxide and/or aluminum hydrates and/or aluminum oxide
hydrates and/or alkali silicates and/or alumosilicates.
WO 2011/020556 A1 and the related patent family also describe an
aluminum or aluminum alloy formed and/or structural part, and a
process for protecting its surface. An anti-corrosion layer
obtained from a sol-gel system is applied directly to the surface
of aluminum or aluminum alloy, without anodized layer, which is to
be produced by integrated hardening or drying during an optimized
process sequence, that is, a shortened process sequence.
An anodized layer is also omitted in EP 2 328 183 A1 and the
related patent family. In a substrate with a metal foil for
preparing photovoltaic cells, a first side of the metal foil is
provided for arranging a photovoltaic-absorber layer. In order to
improve the chemical resistance and the corrosion resistance at
elevated temperature, a protective layer of a silicon-based sol-gel
paint is arranged on the second side of the metal foil.
EP 1 306 467 A1 describes a thermoplastic resin-coated aluminum
plate, wherein the aluminum plate bears a semi-non-porous
conversion layer prepared by a pretreatment. In [0012], the term
"semi-non-porous" is characterized in that the ratio (called
porosity) of the free areas of pores present in the conversion
layer on the surface of the aluminum plate to the total area of the
anodized film is 30% or less. If the porosity is 5% or less, the
film is called practically non-porous. The thickness of this layer
can be within a range of from 50 to 3000 .ANG. (5 to 300 nm).
According to [0031], the conversion layer is coated with a polymer
containing silicon. This polymer has corresponding thermoplastic
properties and is prepared from various silanes or siloxanes as
precursors.
JP 06-316787 A describes the anodization of an aluminum surface by
immersing it into a water-containing alcoholic HCl solution
containing a small amount (<2% by weight) of an alkoxysilane to
obtain a fully sealed conversion layer.
JP 60-179475 A describes the formation of a conversion layer on
aluminum surfaces by applying an inorganic paint containing a high
organosilicon condensate, which lacks silanol groups, however. It
is applied to an aluminum surface anodized in the usual way.
EP 1 780 313 A2 relates to an article, comprising a substrate
having a surface of aluminum or an aluminum alloy, a sealing anodic
coating layer overlying at least part of the substrate, and a layer
of a silicon-containing polymer overlying the anodic sealing layer.
According to the description, the coating is performed directly
with the polymer, or with an aqueous solution of a silane without
performing a cold or hot sealing directly following the preparation
of the conversion layer. In this way, this is also shown in Example
1. However, reference is made to the military specification of the
U.S. Department of Defense (MIL-A-8625F), according to which a
complete sealing for at least 15 minutes (p. 7, items 3.8.1 and
3.8.1.1) is prescribed independently of layer thickness, however.
The applied polymer coating is to be dried at a temperature of from
10 to 100.degree. C.
In the motor vehicle field, there are a number of trim parts having
surfaces of aluminum or aluminum alloys. Thus, WO 2009/068168
describes that the decorative surfaces are obtained by polishing or
electropolishing. the most frequently used aluminum materials that
are employed in the motor vehicle field are also known from this
document. In addition to pure aluminum, these include aluminum
alloys with the material symbols Al 99.85MgSi or AlMg0.5 or 0.8.
The automobile manufacturers expect an alkali resistance of at
least 11.5, and even up to 13.5 for particular components.
Appropriate alkali resistances and other properties of aluminum
surfaces are prescribed, among others, by the manufacturer
Volkswagen AG in their internal, but publicly available, Component
Specification TL182 (issue 2011 January), "Inorganic Protective
Layer on Aluminum Parts".
SUMMARY OF THE INVENTION
The object of the present invention is to provide another process
for preparing components of aluminum or an aluminum alloy having
improved corrosion resistance, especially reaching alkali
resistance up to pH values of 13.5, without adversely affecting the
remaining positive properties of an anodized aluminum surface, such
as corrosion resistance towards salt and acid loads, weathering and
scratch resistance.
The solution to the above object consists in an essential process
step of hot sealing an anodically oxidized surface of aluminum or
an aluminum alloy. After a per se conventional anodizing process
comprising pretreating, anodic oxidation and rinsing steps, the
anodically oxidized surface is only partially hot-sealed, so that a
high porosity of the surface is maintained. Subsequently, this
surface is contacted with a material containing an organosilicon
network former, followed by curing at a temperature of up to
250.degree. C. Too high a curing temperature may cause discoloring
of or detaching from the aluminum surface, which is not accepted by
the purchaser of the component with the aluminum or the aluminum
alloy.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a first embodiment, the invention relates to a process for
treating an anodically oxidized surface of aluminum or an aluminum
alloy by means of a wet chemical process, wherein the surface of
aluminum or of an aluminum alloy is pretreated, anodically
oxidized, rinsed and hot-sealed, characterized in that partial hot
sealing is performed in water at a temperature of up to 100.degree.
C. in the course of up to 30 s/.mu.m of layer thickness of the
conversion layer, followed by contacting a material containing an
organosilicon network former with the partially hot-sealed surface,
followed by curing at a temperature of up to 250.degree. C.
Components prepared according to the invention were subjected to a
salt spray test according to DIN EN ISO 9227. This is a 480 h
neutral salt spray (NSS) test according to DIN EN ISO 9227 NSS, and
a 48 h CASS test according to DIN EN ISO 9227 CASS. The
specification of the component includes that no optical change from
the delivered state must be visible, and detachment of the
protective layer and corrosion on class A or class B surfaces of
the component are not accepted either. The components obtainable
according to the invention showed no optical change, in particular,
no white discoloration, from the delivered state.
In another acid-heat-alkali resistance (AHA resistance) test,
alkali resistance was tested. The sequence of this method is
immersion of the component for 10 minutes into an aqueous solution
with a pH value of 1. This is followed by rinsing with water and
drying. After heat storage for one hour at 40.degree. C., the
component is immersed for 10 min into a solution at pH 13.5. After
subsequent rinsing with water and drying, no optical change from
the delivered state could be noted.
In the so-called convened AMTEC-Kistler and acid-heat-alkali (AHA)
resistance test, the mechanical strength of the component is
measured. The coatings obtainable according to the invention did
not detach.
Also, in the temperature resistance test performed in the course of
24 h at 160.degree. C., no cracks and no optical changes showed as
compared to the delivered state, even though the material applied
to the anodized aluminum or aluminum alloy contained organic
components.
The light and weather resistance tests usual in the motor vehicle
field, such as the Florida test or Kalahari test, could be passed
by means of the present invention.
In addition, components prepared according to the invention passed
a sterilization process of at least 500 cycles as usual in medical
engineering. In each cycle of such a sterilization process, the
component was at first cleaned with water at 40 to 60.degree. C.
for at least 5 minutes. Suitable pH-neutral or alkaline products,
for example, with pH<11.5, may also be employed as cleaners. The
sterilization was subsequently performed with moist heat under
fractionated vacuum (steam sterilization, DIN EN ISO 17665-1) at
134.degree. C., under a pressure of 3 bar, with a holding time of
at least 5 minutes and a drying time of at least 15 minutes per
cycle.
Below, a typical anodizing process is described, which is also
performed according to the present invention, for example, using a
standard alloy, such as Al99.85MgSi.
It is essential that the anodized components, especially trim
parts, in the delivered state are free from polishing defects,
scratches, damages or similar defects that may deteriorate the
appearance of the components, especially trim parts.
In addition, the surface of the component must not exhibit any
dulling, cloudiness, optical changes (for example, blue tinge),
cracking or shadow-like regions, even in a state of use.
Before the treatment or coating, it must be ensured that the
components are free from dust, fingerprints and other residues. The
components must not be touched with bare hands before the treatment
or coating. Any loading of product holders should be done with
gloves of lint-free cloth.
Preferably, as usual in the prior art, the components are first
degreased, subjected to preliminary and final chemical polishing
steps, and deoxidized before the usual anodizing process is
performed, for example, in sulfuric acid with direct current or
alternate current.
Naturally, the aluminum component is rinsed, or spray-rinsed,
between the respective steps.
Suitable methods and specifications for hard anodization can be
found, for example, in Aluminium Taschenbuch, 16th Edition, 2009,
pp. 577 ff. In particular, methods using direct current and
sulfuric acid according to the so-called sulfuric acid anodizing
method are described therein. This disclosure is fully included in
the present invention by reference.
The sealing of anodically produced oxide layers is known from pp.
579 ff. of the above mentioned Aluminium Taschenbuch. It is
described that the anodically produced oxide layer is microporous
and reaches its optimal corrosion resistance only by a sealing
treatment, which causes the pores to be closed. For this essential
pore closure, two basic treatment methods are available, i.e.,
conventional (hydrothermal) sealing and cold impregnation on the
basis of nickel fluoride (cold sealing).
The cold sealing is performed, for example, in a bath of fully
desalted water adding a sealant containing a metal fluoride, for
example, nickel fluoride and/or sodium fluoride, at a temperature
above room temperature (25.degree. C.), for example, at 28.degree.
C. to 32.degree. C., and at a slightly acidic to neutral pH value,
for example, from 6.0 to 7.0, for a few minutes, for example, at
least 4 minutes, as described in WO 2009/068168 A1.
However, the process according to the invention can also be
performed without this cold sealing step, so that both variants are
equally preferred.
According to the invention, hot sealing is employed. The Aluminium
Taschenbuch describes on page 580 that the conventional sealing by
hydrating the oxide layer is as old as the method of anodic
oxidation itself. The oxide layer produced is preferably subjected
to a hot water treatment in fully desalted water with a pH value of
6+/-0.5 at more than 96.degree. C., or to a treatment with
saturated steam of above 98.degree. C. According to this, the
treatment time is usually 3 to 4 min/.mu.m of layer thickness. The
oxide layer is superficially dissolved during the sealing process.
Any adsorbed anions from the anodizing bath are dissolved thereby.
Because of the increase in pH value that takes place, aluminum
hydroxide gel deposits on the surface, where it crystallizes. A
conversion of the oxide to boehmite takes place in this
process.
According to the invention, this process step of hot sealing is
particularly important. Here too, hot sealing is preferably
performed in the above mentioned temperature frame, but a
significantly shorter sealing time is realized according to the
invention. It is particularly preferred according to the present
invention to perform the partial hot sealing in water at a
temperature of more than 96.degree. C., especially at up to
100.degree. C., in the course of up to 30 s/.mu.m, especially up to
20 s/.mu.m, of layer thickness of the conversion layer. At this
time, the pores of the anodized surface are not yet completely
closed and can partially take up in the surface the material
containing the organosilicon network former. This causes an
excellent anchoring of this material in and on the conversion layer
including the advantageous properties described above.
As set forth above, the pretreatment of the process according to
the invention includes, in particular, degreasing, rinsing,
pickling, rinsing, polishing, rinsing, acid treatment and rinsing,
before the actual anodic oxidation.
Then, after the anodic oxidation and the hot sealing, the material
containing the organosilicon network former is contacted with the
anodically oxidized surface. This may be done, for example, by flow
coating, dipping, spraying, rolling, knife coating and/or roller
coating. It is also possible to charge the material and/or the
substrate electrostatically before and/or during the
contacting.
According to the invention, a material containing an organosilicon
network former is employed. It may preferably be selected from the
group of non-fluorinated silanes, especially
CH.sub.3Si(OC.sub.2H.sub.5).sub.3,
C.sub.2H.sub.5Si(OC.sub.2H.sub.5).sub.3,
CH.sub.3Si(OCH.sub.3).sub.3, C.sub.6H.sub.5Si(OCH.sub.3).sub.3,
C.sub.6H.sub.5Si(OC.sub.2H.sub.5).sub.3,
CH.sub.2.dbd.CHSi(OOCCH.sub.3).sub.3,
CH.sub.2.dbd.CHSi(OCH.sub.3).sub.3,
CH.sub.2.dbd.CHSi(OC.sub.2H.sub.5).sub.3,
CH.sub.2.dbd.CHSi(OC.sub.2H.sub.4OCH.sub.3).sub.3,
CH.sub.2.dbd.CHCH.sub.2Si(OCH.sub.3).sub.3,
CH.sub.2.dbd.CHCH.sub.2Si(OC.sub.2H.sub.5).sub.3,
CH.sub.2.dbd.CHCH.sub.2Si(OOCCH.sub.3).sub.3,
CH.sub.2.dbd.C(CH.sub.3)COOC.sub.3H.sub.7Si(OCH.sub.3).sub.3,
CH.sub.2.dbd.C(CH.sub.3)COOC.sub.3H.sub.7Si(OC.sub.2H.sub.5).sub.3,
(C.sub.2H.sub.5O).sub.3SiC.sub.6H.sub.4NH.sub.2,
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6NH.sup.2,
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6CN,
(CH.sub.3O).sub.3SiC.sub.4H.sub.8SH,
(CH.sub.3O).sub.3SiC.sub.6H.sub.12SH,
(CH.sub.3O).sub.3SiC.sub.3H.sub.6SH,
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6SH,
(CH.sub.3O).sub.3SiC.sub.3H.sub.6NHC.sub.2H.sub.4NH.sub.2,
(CH.sub.3O).sub.3SiC.sub.3H.sub.6NHC.sub.2H.sub.4NH.sub.2,
##STR00001##
Alternatively or cumulatively, fluorinated silanes, especially
CF.sub.3CH.sub.2CH.sub.2SiY.sub.3,
C.sub.2F.sub.5CH.sub.2CH.sub.2SiY.sub.3,
C.sub.4F.sub.9CH.sub.2CH.sub.2SiY.sub.3,
n-C.sub.6F.sub.13CH.sub.2CH.sub.2SiY.sub.3,
n-C.sub.8F.sub.17CH.sub.2CH.sub.2SiY.sub.3,
n-C.sub.10F.sub.21CH.sub.2CH.sub.2SiY.sub.3, where Y represents
OCH.sub.3 and/or OC.sub.2H.sub.5, may also be employed in the same
way. The material as defined herein is preferably employed with a
low solvent content, especially free from solvent. However, if
appropriate, the material may also contain solvents or dispersants.
According to the invention, the above mentioned silanes are
cross-linked on the partially sealed conversion layer by a sol-gel
process. This material has no thermoplastic properties during and
after the sol-gel process, even if the sol-gel process was started
before the contacting.
It is particularly preferred according to the present invention to
perform the curing of the material containing an organosilicon
network former at an aluminum-protecting temperature within a range
of from 120 to 250.degree. C., especially to 200.degree. C. The
sol-gel process causes an excellent curing that brings about the
above mentioned properties, although the coating is extraordinarily
thin and has a layer thickness as low as in the nanometer range,
but also up to a few micrometers. Because of the incomplete closure
of the pores, the uncured material permeates into the conversion
layer and is also chemically bonded to it. In this process step,
the conversion layer is further densified.
In contrast, what is much thicker is the anodically produced
conversion layer itself, whose layer thickness is preferably from 5
to 15 .mu.m, more preferably from 7 to 10 .mu.m. Because of the
extraordinarily low thickness of the cured material containing an
organosilicon network former on and in the surface of the
conversion layer, it contains Al--O--Si-bonded
organosilicon-functional silicates. Thus, the above mentioned
material is chemically bonded in and to the conversion layer and
thus leads to an extraordinarily high adhesive strength of the
latter, which naturally does not have any thermoplastic
properties.
The term "aluminum surface" within the meaning of the present
invention includes any aluminum substrates, for example, the alloys
described in EP 1 780 313 A2 in [0009] as well as the pure metal.
The aluminum surfaces obtainable according to the invention may
naturally have a colorless and/or colored surface. In a case where
the surface should be colored, this can be integrated into the
anodizing process or into the coating process in accordance with
the process usual in the prior art.
The anodically oxidized surfaces obtainable according to the
invention may occur in a wide variety of forms, for example, in the
form of facades, window frames, door frames, fitting parts and trim
strips in construction, in vehicle construction and in the
furniture industry, rims, household appliances, signs, lighting
elements, furniture components, machine elements, handles,
construction parts, fixtures or engine components and heat
exchangers, for example, for air conditioning systems in vehicles
or buildings. The components according to the invention may also be
employed in the field of medical engineering, in which disinfecting
methods are frequently employed. These components meet the
manufacturer's specifications if they are treated, for example,
with ozone, steam or hydrogen peroxide.
EXAMPLE
Example 1
An aluminum component of Al99.85MgSi anodized according to the
prior art (Aluminium Taschenbuch loc. cit.) and initially sealed
(partially sealed) for 30 seconds in hot water of >96.degree. C.
was stored under a standard laboratory atmosphere for another 24
hours after rinsing and drying. A conversion layer having a
thickness of 7.5 .mu.m was obtained.
Thereafter, this partially sealed component was dipped into a
composition of 58.80 g of tetraethoxy orthosilicate, 24.90 g of
[3-(2,3-epoxypropoxy)propyl]trimethoxysilane, 25.17 g of fully
desalted water and 2.13 g of 32% hydrochloric acid, which had been
diluted with a mixture of 184.53 g of 2-propanol and 3.72 g of
fully desalted water, and withdrawn so slowly that a visible wet
film remained recognizable on the component during the withdrawal.
After an air drying time of 10 minutes, the component was heated in
a convection oven at 200.degree. C. for one hour, and the anodized
layer added with silicate was finally sealed and cured.
The total layer thickness of the conversion layer including the
silicate layer was about 8.5 .mu.m.
Example 2
An aluminum component of Al99.85MgSi anodized according to the
prior art (Aluminium Taschenbuch loc. cit.) with a conversion layer
having a thickness of 7.5 .mu.m was partially sealed in hot water
of >96.degree. C. for 3 minutes (24 seconds/.mu.m of conversion
layer). After rinsing and drying, the component was stored under a
standard laboratory atmosphere for another 24 hours.
Thereafter, this partially sealed component was dipped into a
composition of 58.80 g of tetraethoxy orthosilicate, 24.90 g of
[3-(2,3-epoxypropoxy)propyl]trimethoxysilane, 25.17 g of fully
desalted water and 2.13 g of 32% hydrochloric acid, which had been
diluted with a mixture of 184.53 g of 2-propanol and 3.72 g of
fully desalted water, and withdrawn so slowly that a visible wet
film remained recognizable on the component during the withdrawal.
After an air drying time of 10 minutes, the component was heated in
a convection oven at 200.degree. C. for one hour, and the anodized
layer added with silicate was finally sealed and cured. The total
layer thickness of the conversion layer including the silicate
layer was about 8.5 .mu.m.
A component treated according to Example 1 or 2 passed the
following test:
The testing was done at a temperature of 23.degree. C. The
subsequent tests were performed successively on the same component
in the order given.
Sequence: dipping in solution of pH 1 for 10 min; rinsing in fully
desalted water and drying, heat storage for 1 h at 40.degree. C.
(further test sequence without cooling), dipping in solution of pH
13.5 for 10 min; rinsing in fully desalted water and drying.
No optical change from the original state could be seen.
Test solution defined by calculation:
pH 1: 0.1 M aqueous hydrochloric acid
pH 13.5: buffer solution of 12.7 g of sodium hydroxide, 4.64 g of
sodium phosphate dodecahydrate (corresponding to 2 g of sodium
phosphate), 0.33 g of sodium chloride (corresponding to 200 mg of
chloride), dissolved in 1 liter of water.
Comparative Example 1
An aluminum component of Al99.85MgSi anodized according to the
prior art (Aluminium Taschenbuch loc. cit.) with a conversion layer
having a thickness of 7.5 .mu.m was sealed in hot water of
>96.degree. C. for 30 minutes. After rinsing and drying, the
component was stored under a standard laboratory atmosphere for
another 24 hours.
Thereafter, this sealed component was dipped into a composition of
58.80 g of tetraethoxy orthosilicate, 24.90 g of
[3-(2,3-epoxypropoxy)propyl]trimethoxysilane, 25.17 g of fully
desalted water and 2.13 g of 32% hydrochloric acid, which had been
diluted with a mixture of 184.53 g of 2-propanol and 3.72 g of
fully desalted water, and withdrawn so slowly that a visible wet
film remained recognizable on the component during the withdrawal.
After an air drying time of 10 minutes, the component was heated in
a convection oven at 200.degree. C. for one hour, and the anodized
layer added with silicate was cured. The total layer thickness of
the conversion layer including the silicate layer was about 8.5
.mu.m.
A component treated in this way failed the testing according to the
Examples. An optical change from the original state could be seen.
The component had undergone discoloration to white.
Comparative Example 2
An aluminum component of Al99.85MgSi anodized according to the
prior art (Aluminium Taschenbuch loc. cit.) with a conversion layer
having a thickness of 7.5 .mu.m was sealed in hot water of
>96.degree. C. for 15 minutes. After rinsing and drying, the
component was stored under a standard laboratory atmosphere for
another 24 hours.
Thereafter, this sealed component was dipped into a composition of
58.80 g of tetraethoxy orthosilicate, 24.90 g of
[3-(2,3-epoxypropoxy)propyl]trimethoxysilane, 25.17 g of fully
desalted water and 2.13 g of 32% hydrochloric acid, which had been
diluted with a mixture of 184.53 g of 2-propanol and 3.72 g of
fully desalted water, and withdrawn so slowly that a visible wet
film remained recognizable on the component during the withdrawal.
After an air drying time of 10 minutes, the component was heated in
a convection oven at 200.degree. C. for one hour, and the anodized
layer added with silicate was cured. The total layer thickness of
the conversion layer including the silicate layer was about 8.5
.mu.m.
A component treated in this way failed the testing according to the
Examples. An optical change from the original state could be seen.
The component had undergone discoloration to white.
Comparative Example 3
An aluminum component of Al99.85MgSi anodized according to the
prior art (Aluminium Taschenbuch loc. cit.) with a conversion layer
having a thickness of 7.5 .mu.m was not sealed. After rinsing and
drying, the component was stored under a standard laboratory
atmosphere for another 24 hours.
Thereafter, this component was dipped into a composition of 58.80 g
of tetraethoxy orthosilicate, 24.90 g of
[3-(2,3-epoxypropoxy)propyl]trimethoxysilane, 25.17 g of fully
desalted water and 2.13 g of 32% hydrochloric acid, which had been
diluted with a mixture of 4019 g of 2-propanol and 82 g of fully
desalted water, and withdrawn so slowly that a visible wet film
remained recognizable on the component during the withdrawal. After
an air drying time of 10 minutes, the component was heated in a
convection oven at 200.degree. C. for one hour, and the anodized
layer added with silicate was finally sealed and cured. The total
layer thickness of the conversion layer including the silicate
layer was less than 8.5 .mu.m and was substantially the same as the
original layer thickness.
A component treated in this way failed the testing according to
Examples 1 and 2. An optical change from the original state could
be seen. The component had undergone discoloration to white.
* * * * *
References